The Design And Light Extraction Efficiency Pproperty Of The Surface Micro-nano Structure On GaN-based LED

As the global environmental pollution and energy crisis intensify,energy conservation and emission reduction have become an effective method to solve the current environmental and energy problems.Light-emitting diodes(LED),a new type of green lighting source with many advantages,have been widely used by people.The research of gallium nitride(Ga N)-based LEDs has attracted the attention of scholars all over the world especially.At present,the large-scale commercialization of LEDs is limited in addition to the cost problem,that is,its light extraction efficiency is not high.This is because the photons generated in the device caused by total reflection and Fresnel reflection can't be effectively extracted.We know that by improving the internal quantum efficiency and external quantum efficiency of the LED,the light extraction efficiency can be improved,however the internal quantum efficiency has reached a higher value,so how to improve the light extraction efficiency of the LED becomes very important.In order to solve the above problems,domestic and foreign scholars have proposed technologies such as chip flip chip,pattern substrate,surface plasmon,micro-nano structure,etc.to improve the light extraction efficiency of LEDs.Among them,the surface microstructure has the advantages of simple operation and easy realization.Makes more researchers invest in related experiments and achieved remarkable results.In previous studies,we found that the use of zinc oxide(ZnO)micronano structure grown on the surface of Ga N-based LEDs can improve the light extraction efficiency of the LED to a certain extent,but for the selection of the parameters of the ZnO micro-nano structure and the effect of each parameter on the light extraction efficiency The impact of the lack of systematic research.Therefore,this paper is based on the finite difference time domain method(FDTD),using Rsoft software to design ZnO micro-nano structures with different structural parameters,thereby increasing the Ga N-based LED's escape light cone and improving its light extraction efficiency.At the same time,the influence of different micro-nano structures on the light extraction efficiency is analyzed.The main research contents and results of this paper are as follows:(1)Design a ZnO micro-nano structure with square and triangular lattices,and use Band Solve module to analyze its band characteristics.Design columnar and porous ZnO micro-nano structures,and use Band Solve module to analyze its energy band characteristics.The simulation analysis results show that the triangular lattice and columnar ZnO micro-nano structure have a larger band gap,which is more conducive to photon escape.(2)Using the Full Wave module,the influence of ZnO micro-nano structure on the light extraction efficiency of Ga N-based LEDs was studied based on FDTD.Four surface ZnO structures of micro-nano spherical,cylindrical,conical and quadrangular pyramid were designed respectively,and the height,period,diameter and other parameters of ZnO were optimized by the controlled variable method.The simulation analysis results show that the four ZnO micro-nano structures can improve the light extraction efficiency of Ga N-based LEDs to a certain extent,the spherical structure has weaker promotion effect,and the cylindrical structure has the best promotion effect.(3)Use the Diffract MOD module to simulate and analyze the transmission spectrum of Ga NLED with ZnO micro-nano structure.The Full Wave module is used to simulate and analyze the electromagnetic field and far-field radiation pattern of Ga N-LED with ZnO micro-nano structure.The simulation results show that the micro-nano structure can increase the light escape angle,so that more energy is radiated to the outer space to improve the light extraction efficiency.The above simulation analysis work has guiding significance for the research of improving the light extraction efficiency of Ga N-based LEDs through the surface ZnO micro-nano structure,and provides a reference for subsequent experimental design and preparation of LEDs.